Apparatus for sizing and cutting strip core material



Nov. 30, 1965 w. OLSEN ETAL 3,220,291

APPARATUS FOR SIZING AND CUTTING STRIP CORE MATERIAL Original Filed Nov. 13, 1961 3 Sheets-Sheet 1 INVENTOR N\L.LY OLSEN BY umr n D'TINDHLL n TToRnlEV Nov. 30, 1965 w. OLSEN ETAL 3,220,291

APPARATUS FOR SIZING AND CUTTING STRIP CORE MATERIAL Original Filed Nov. 13, 1961 3 Sheets-Sheet 2 1 3| 3 2| k 4/ 1 F F l I INVENTOR.

WILLY OLSEN BY HOWARD D. TINDHLL A TTOR/VFK Nov. 30, 1965 w. OLSEN ETAL 3,220,291

APPARATUS FOR SIZING AND CUTTING STRIP CORE MATERIAL 3 Sheets-Sheet 5 Original Filed Nov. 13, 1961 IN VEN TOR.

OLSEN WILLY BY Howl-'29 o TIHDA LL.

/ ATTORNEY United States Patent 3,220,291 APPARATUS FOR SIZING AND CUTTING STRIP CORE MATERIAL Willy Olsen and Howard D. Tindall, Lynchhnrg, Va., as-

signors to H. K. Porter Company, Inc., Lynchhurg, Va, a corporation of Delaware ()riginal application Nov. 13, 1961, Ser. No. 151,655. Divided and this application Oct. 3, I963, Ser. No.

3 Claims. (cl. 83-236) This invention relates generally to wound type transformer cores, and more particularly relates to a wound transformer core having superior magnetic characteristics resulting in lower core losses and higher transformer efficiency, this application being a division of copending application Serial No. 155,655, filed November 13, 1961.

The superiority of a wound transformer core as compared to cores made of solid sections or punched laminations is well-known to workers in the art and need not be detailed herein. Moreover, it is also known that a wound transformer core made from a single continuously wound strip of core material will normally exhibit better magnetic properties than a transformer core fabricated from a plurality of strips which have ends butted or lapped to form the composite core. However, as a practical matter, manufacturing economics dictate wound cores should be made from a plurality of strips of core material rather than from a single continuous strip even though the joints inherent in such a construct-ion tend to degrade the magnetic efiiciency of the core structure. This being the case, a great deal of effort has been concentrated on ways of minimizing the deleterious etfects of the joints while maintaining the manufacturing benefits which flow from the jointed type of core construction.

In nearly all instances it is desirable to form the transformer cores so that they are of rectangular or square shape and have a corresponding rectangular or square central opening or window to accommodate the transformer coil structure in order that the overall transformer may be made as compact as possible, the composite transformer usually including at least two cores each of which is disposed about one leg of the coil structure so that one leg of each core is disposed within the coil window in such manner as to cause the coil window to be substantially completely filled. This general type of transformer structure creates problems with regard to the installation of the preformed cores through the coil window since there is very little unoccupied coil window space in the finished assembly and the corners of the core structures must be passed through the window in order to close the core.

The preformed core corners are necessarily deformed by straightening in order to be passed through the window, particularly with regard to the outer laminations of the cores, with the consequent introduction of mechanical stresses and strains into the laminations of the cores. The introduced stresses alter the magnetic properties of the core in an adverse manner and are of course undesirable. This condition is aggravated in most wound core constructions by the fact that the core laminations have a high space factor at the corners and are prevented from readily shifting relative to one another as they are stressed while being passed through the coil window. This increases the strains introduced at the corners and further degrades the core performance. Attempts have been made in the past to reduce the severity of this problem by the use of various forming methods directed toward reducing the space factor at the corners, as for example by the use of insert shims in the corner regions as the core is being wound. Unfortunately, these known methods are either uneconomic or also tend to reduce the space factor in the straight sided legs and yoke regions of the core where a high space factor is desirable. As will be subsequently seen, the physical realizability of the desirable core structure according to the invention is related to the method by which the core is made, and the novel method employed to produce the cores to be hereinafter described is a contributing factor to the superior performance of which these cores are capable. According- 1y, it is a primary object of this invention to provide a wound transformer core of rectangular or square form characterized by a high space factor throughout the straight sided regions of the core, and a space factor at the corners of the core which is sufficiently low that it allows for relatively free interlaminar movement during assembly of the core to its coil structure to thereby prevent the creation of mechanical stresses and strains in the core material and preserve the magnetic properties of an unstressed core.

Another object of this invention is to provide a wound core as aforesaid which is built up of core sections each of which is openable along one side leg thereof but wherein all of the core sections are not openable along the same leg of the built core.

Yet another object of this invention is to provide a novel wound core structure which is built up from a plurality of internested core sections, and wherein the innermost core section acts as a form for the additional core sections built up thereupon.

Still another object of this invention is to provide a novel wound core structure built up of a plurality of core sections each including several laminations of one turn each with their ends disposed in staggered relationship so that closure of the core section forms a plurality of successively offset butt joints in the region of closure.

A further object of this invention is to provide a novel wound transformer core construction as aforesaid wherein the ends of the inner and outer laminations of the core sections are offset from the ends of the immediately adjacent laminations in the same core section by an amount substantially greater than the offset of the ends of the laminations lying between the inner and outer laminations to thereby insure proper mating closure of the ends of each core section.

Another object of this invention is to provide a novel method of making the wound cores according to the invention, and to provide novel apparatus for implementing the method.

The foregoing and other objects of the invention will become clear from a reading of the following specification in conjunction with an examination of the appended drawings, wherein:

FIGURE 1 illustrates a typical wound core according to the invention showing the high space factor in the straight core portions and the relatively lower space factor at all of the corners, and also illustrating the fact that all of the sections from which the core is built up, excepting the innermost section, are jointed along one of the straight side legs of the core, the innermost section being jointed on the opposite core leg;

FIGURE 2 is an enlarged fragmentary showing of the stepped butt joint construction of a typical core section;

FIGURE 3 illustrates a pair of core sections built through the window of a typical coil structure and illus trating the manner in which the sections are built upon one another to form a complete core;

FIGURE 4 illustrates an enlarged fragmentary view of a core section joint in which an improper closure condition may occur when the ends of the laminations are offset from one another by equal amounts;

FIGURE 5 illustrates an increased offset of the ends 3 of the inner and outer laminations of a core section by means of which it-may be readily determined when a proper closure of the joint has been effected;

FIGURE 6 illustrates a complete core section having laminations whose ends are ofiset in a manner illustrated in FIG. 5, the joint being illustrated in a partially opened condition for clarity of viewing;

FIGURE 7 illustrates in perspective view a lamination sizing and cutting apparatus which feeds the core strip material into a sizing jig and cuts each strip to proper size;

FIGURE 8 is an enlarged fragmentary longitudinal vertical sectional view through the apparatus of FIG. 7 as would be seen when viewed along the line 88 thereof;

FIGURE 9 is an enlarged fragmentary plan view of the sizing jig portion of the apparatus of FIG. 7 as would be seen when viewed along the line 99 thereof;

FIGURE 10 is a vertical sectional view through the jig structure of FIG. 9 as would be seen when viewed along the line 1ll-lll thereof;

FIGURE 11 illustrates two strips of material bent into surface engaged concentric circles with their opposite ends respectively abutted, certain geometric relationships being derivable therefrom;

FIGURE 12 illustrates the utilization of the relationships derived from FIGURE 11 for the purpose of constructing a core strip sizing jig; and

FIGURE 13 illustrates in side elevation a stack of laminations previously cut in the apparatus of FIG. 7 with their righthand ends displaced from one another preparatory to being bent into a circular loop as one step in the preparation of the core according to the invention.

In the several figures, like elements are denoted by like reference characters.

Turning now to a consideration of the drawings, there will be seen in FIGURE 1 a composite core made up of a plurality of internested individual core sections, the inner and outer sections being designated respectively as 21 and 34 while various of the intermediate sections have been designated as 22, 23, and 24. The core is for purposes of illustration shown as of generally rectangular form having a pair of side legs 26 and 27 and a pair of yoke portions 28, the straightsided legs and yoke portions of the core being joined by the corner regions which are so formed that gaps are observed to intervene the adjacent core sections. In actuality, there also exist slight gaps between the individual laminations of each core section in the corner regions thereof although these are not clearly visible because they would tend to confuse rather than clarify the drawing. The inside periph cry of inner core section 21 defines a window 29 within which one leg of the transformer coil structure is disposed in a completed transformer unit.

It should be observed that while the corners 21a of the innermost lamination of the transformer core are rather sharply defined, all of the remaining laminations of the core are of smoothly curved configuration in the corners thereof, the radii of the corner curvature of the laminations increasing outwardly from the innermost lamina- Lion. The curvature of the core section corners com bined with the interlaminar gaps in the corner regions allow relative movement between adjacent laminations when the core is being built up section by section upon a coil structure, and prevents mechanical strains from being induced in the laminations and thereby preserves the magnetic characteristics of the core.

By means of a method to be subsequently set forth herein, the looseness in the corners can be controlled to provide a corner space factor in the preferred region of 85% to 95% with an optimum space factor obtaining at about 90%. In contrast to this, wound cores made by the usual methods heretofore known result in core corners having space factors of 96% to 98%, resulting in a corner structure which for all practical purposes is the same as if the corners were rigidly clamped because such high values of space factor prevent corner flexing unless a considerable corner opening force is applied. The necessity for applying such high forces in normal core constructions to effect insertion of the core sections through the window of the coil structure sets up substantial mechanical stress and strain in the corner regions which adversely affect the core magnetic characteristics.

Additionally, it will be appreciated that the usual wound core characterized by a high corner space factor is not completely strain relieved by the usual annealing process. This is so because even though it is true that a core during the annealing process may be strain relieved because of longitudinal expansion of the laminations while they are hot, nevertheless, when the annealed core is cooling down, the outer laminations are..those which cool first and are attended by contraction of these laminations which exert a compressional force upon the not as yet cooled inwardly lying laminations and cause the latter to buckle so that a wavy condition is produced in the legs and yoke portions of the core. This waviness is of course highly undesirable and tends to reduce the space factor in the legs and yoke portions of the core, which are precisely those portions of the core in which a high space factor is desired. No such undesired condition occurs in wound cores made according to the present invention, the space factor achieved in the legs and yoke portions being very close to As best seen in FIGURE 2, the laminations 30 of each of the individual core sections, such as for example core section 24, close into abutting relationship as at 31, and the ends of the laminations adjacent to one another are relatively offset a distance designated in FIGURE 2 as the distance L, so that a staircase type of composite joint for the core section is formed. These joints are shown in FIGURE 1 for example as 21b, 22b, and 23b for the respective core sections 21, 22, and 23. Additionally it will be observed that the core section joints 22b and 2312 are longitudinally offset within the core side leg 27 and that this relationship holds for the remainder of the core section joints extending outward through the core side leg 27 to the outer section 34. Thus, the offset joints of the several internested core sections are distributed lengthwise of the core leg 27 to minimize the magnetic reluctance across a plane extending perpendicularly transversely through the leg 27 with the core overall joint length being greater than the thickness of the core leg 27 in which the joint is located. Significantly, it will be observed that the joint 21b for the core section 21 does not lie in the leg 27 but is disposed within the core leg 26. The significance of this feature is most clearly seen from the showing of FIGURE 3 to which attention should be now directed.

In FIGURE 3 there will be seen a transformer coil structure having a pair of legs 32 and 33, the leg 32 being disposed within the window of the lefthand core structure 2% and the leg 33 being disposed within the window of a second righthand core structure 20' shown in partly assembled condition. It will be observed that the window 35 of the coil structure is substantially filled by the completely assembled side leg 27' of the lefthand core structure 20 and the assembled sections of the leg 27' of the righthand core 26), there remaining sufficient space for insertion of the ends 36 of the outer core section-34 of the righthand core. It will be appreciated that by assembling the individual core sections so that the section gaps are disposed within the window 35 of the coil structure, it is only necessary to feed straight portions of the core section into the window.

Stated somewhat differently, excepting for the innermost section, it is not necessary to pass any of the core section corners through the coil structure window. Obviously, in the illustrated case of FIGURE 3 no core section corner could passthrough the window without being practically completely straightened out, the necessity of doing which would cause the severe mechanical strains and stresses in the core material corners previously discusses. Nevertheless, this is exactly What is done in the assembling of most known types of core structures because these cores are almost always constructed so as to be openable through the core yoke region or through the core leg corresponding to those designated as 26'. The difiiculty of passing a core section corner through the coil window becomes increasingly more acute as the window size is reduced due to the buildup of the core structure.

It will be observed however in both the showings of FIGURE 1 and FIGURE 3 that the innermost core sections 21 and 21 respectively each has a gap region disposed in the leg opposite to that in which the gap regions of the other core sections are placed. The reason for this is that since the inner core section is in effect the form on which the remainder of the core sections are placed and determines the initial size of the core window, it is almost essential that there should be a guarantee that the gap of the inner core section be completely and properly closed. By placing the gap of the inner section on the outside of the coil leg, and not in the window, such proper closing of the gap can be assured since the joint is clearly visible and easily manipulable when placed in this location. Further, this orientation of the inner core section joint does not pose a real problem with regard to the installation of the inner core section about the coil form because the coil structure window is completely open at this time and the coil section corners may be rather easily passed therethrough without any material flexing or straightening thereof, so that the mechanical stress situation, which becomes progressively worse as the cores are built up, does not really exist for the innermost core section.

While FIGURE 3 shows the typical core sections as being each composed of four laminations, this is by no means a necessary condition or limitation and the individual core sections may be formed with as many laminations as are deemed desirable. In this regard, FIGURE 2 illustrates the core section 24 as being built up of laminations, whereas FIGURES 4, 5 and 6 illustrate core sections as being built up of eight laminations. Moreover, it is not necessary that all of the core sections of any given composite core should contain the same number of laminations.

During the process of building up a composite transformer construction by installation of the core sections to the coil structure, as for example seen in FIGURE 3, it will be appreciated that as the window of the coil structure becomes progressively smaller due to installation of successive core sections, it becomes progressively more diflicult for the assembler to be certain that the joints of each section have properly closed and that an offset condition such as that shown in FIGURE 4 has not occurred. In FIGURE 4 it will be observed that an improper closure of the joint has occurred due to offsetting of the ends of laminations 3t) so that the ends 31a and 31b of the inner and outer laminations are not in abutment with the opposite ends of the particular lamination of which they form a part. The window area of such an improperly closed joint is of course somewhat larger than it should be, and the various laminations of adjacent-core sections may not be in as close contact as they should be. Also, when the laminations are not each properly aligned, additional strains and stresses are induced in the core structure. Further, the space factor is lowered and the operation of the core is adversely affected due not only to the lowered space factor but also due to the actual reduction of the core cross-section in the region of the improperly closed joint.

This type of undesirable condition can even arise in those cases Where the core section is properly installed and the joint completely closed by virtue of the fact that when the installer removes his hands from the core section which has just been placed about the soil there is a tendency for a slight springback to occur and the joint then opens sufficiently to fall into the condition shown in FIGURE 4. When the next core section is then installed it is quite possible for this condition to go undetected because the outer core section will have sufficient llooseness in the corners to permit a closing of its own joint. Consequently the finished core structure will not be as efficient as it could be. This undesirable condition may be eliminated by forming each core section so that its joint structure takes the form of the preferred embodiment illustrated in FIGURES 5 and 6.

FIGURE 5 illustrates a typical core section generally designated as 37 having inner and outer laminations 38 and 39 and a plurality of intermediate laminations 40. The ends of the intermediate laminations 40 are longitudinally offset relative to one another by a predetermined fixed amount to provide a regular stepped arrangement of the lamination individual butt joints. However, the inner and outer laminations 38 and 39 are observed to each have their ends ofi'set relative to the next adjacent intermediate lamination 40 by an amount substantially in excess of the regularly occurring offset of the ends of the intermedaite laminations relative to each other. With such an arrangement it will be appreciated that any springback which may take place when the core section is assembled into the coil window will not permit the ends of the laminations to become laterally shifted relative to one another because any such springback is insufiicient to cause the ends of the laminations 38 and 39 to override the ends of the next adjacent inner laminations. Therefore, when the next core section is placed .in position by the assembler and its joint is closed, the joint of core section 37 will itself close properly as shown in FIGURE 5.

Understanding now the novel structure of the wound transformer core according to the invention, the method of assembling such a core into an associated coil structure and the improved performance of which the core is capable, attention should now be directed to the re- ,mainder of the figures for an understanding of the method of making the novel core structure and the apparatus employed for carrying out the method.

Each of the rectangular core sections which together make up the composite core shown in FIGURE 1 is made from a plurality of pre-cut straight strips of core material of graduated length. The strips are stacked and bent into a circle with the shortest strip occupying the inside position in the loop and with the longest strip occupying the outside position in the closed loop. The loop sections are then placed in a press and the circular cross-section of the core is then formed into a rectangular section. The formed core is then annealed and disassembled section by section for subsequent installation onto a coil structure.

A part of the apparatus utilized in the making of the cores is a jig structure which includes an angle block 41 illustrated in FIGURES 7 through 10. The angle block 41 is provided with a sloping underface 42 which slants upward from a horizontal bed 43 of the strip sizing and cutting apparatus designated generally as 44 and shown in some detail in FIGURE 7. The angle which the underface 42 of the block 41 makes with the horizontal bed 43 is quite important since it is this angle which determines the difference in length of successively cut strips of core material. There exists a critical angle of orientation which when employed causes successively cut strips to be stackable and formed into a circle so that opposite ends of each strip in the stack will exactly abut one another. Orientation angles larger than the critical angle reduce the difference in length between successively cut strips and prevent abutment of the ends of all laminations disposed radially outward of the innermost lamination when all of the strips are bent into a circular connitude of the critical angle may be determined in the following manner.

Referring to FIGURE 11 there will be seen a pair of strips S and S each of thickness T and folded into internested circular form with the ends of each strip brought into abutment. The strip S has a mean diameter D and a mean circumference C while the strip S has a mean diameter D and mean circumference C The strips S and S of course correspond to any two adjacent laminations of the core to be constructed, these laminations being in circular form in the configuration assumed prior to rectangular forming. It is apparent that the strip S must be longer than the strip S in order that its ends shall be able to close, and it is necessary to determine what the difference in strip length should be so that successive strips of properly increasing length may be cut to form the core. The difference in length between the strips S and S is the difference between their mean circumferences C and C The mean circumference of S is,

whereas the mean circumference of S is,

From this last relationship it is observed that the difference in length AC between any two laminations is a function of the lamination thickness T, which is what one would expect. What is not apparent is that a simple device may be constructed which eliminates the necessity for the calculation of a continuous series of numbers which will be different for each different thickness of core material which it is desired to use. The geometric relationship illustrated in FIGURE 12 provides the basis for the construction of the jig angle block 41, previously referred to, which automatically establishes the proper dilference in length between successively cut strips of core material independently of the strip thickness.

In FIGURE 12 it will be observed that the horizontal line 45 and the upwardly inclined line 46 define therebetween an acute angle Also shown are a pair of rectangles 47 and 47a each of which is of a height designated as T. The lefthand end of the rectangle 47a is positioned to the right of the lefthand end of the rectangle 47 by an amount equal to 272' or 21r times the height of either of the rectangles. The inclined line 46 is pivoted about the apex 48 of the angle 0 until it is tangent to the upper lefthand corners of the rectangles 47 and 47a, as illustrated at 49 and 50. Thus,

It should be noted that the tangent function of 9 is a constant, and hence the angle 0 is completely independent of the height T of the rectangles 47 and 47a. By considering the rectangles 47 and 47a of FIGURE 12 to be the ends of any two core lamination strips each of thickness T, and recalling from the relationship developed from FIGURE 11 that the difference in length between successively cut strips should be 21rT to obtain a proper closure of the joints, it will be now appreciated that an angle block jig may be constructed for the proper sizing of successive strips of core material. However, since the critical angle 0 defines the jig block angle which theoretically results in exact abutment of opposite ends of each lamination of a stack bent into circular form together with the maintenance of complete surface to surface contact between adjacent laminations, it will be appreciated that when the circular stack is rectangularly formed there would exist a 100% space factor at all points of the core cross-section. Since the novel core construction according to the invention is characterized by looseness in the corners, it is necessary that the difference in length between successively cut strips should be slightly longer than that which would result from the utilization of a jig inclined at the derived critical angle 0 This is achieved by reducing the actual angle of the jig block below the critical angle, an actual angual of approximately 8 /2" having been found to be satisfactory.

By so reducing the angle 0 of the jig block to below its critical value, there is obtained a degree of looseness between successive strips in the laminated core structure sufficient to render differences in length of the successive strips inconsequential due to variations in thickness thereof. As will be apparent, the essential requirement is that each lamination strip forming a turn of the core be properly butt-jointed and by providing suflicient looseness between successive turns, minor variations in the lengths of the strips due to thickness variations will not prevent proper butt-jointing of their ends but instead will result only in varying in minor degree the looseness be tween certain successive turns of the core structure.

Returning now to FIGURES 7 through 10, there will be seen the strip sizing and cutting apparatus designated generally as 44 having a remote end section 51 within which is rotatably held a coil 52 of core strip material 53. The strip material 53 is fed off of the roll and over a roller feeder 54 to a vertically reciprocable shear 55, the strip material 53 being fed from the coil 52 at a rate sufficient to form the same into a loop 56 prior to entering the shear in order to maintain a positive longitudinal forward bias tending always to force the forward end of the strip against the sloping underface 42 of the jig angle block 41 secured upon the near end section 57 of the apparatus 54. The bed 43 upon which the strip material is fed into the jig block 41 is formed from a pair of I-bars 58 disposed parallel to one another and spaced apart in the manner best seen in the showing of FIGURE 10. The underside marginal edges of the jig angle block 41 are seated upon the upper flanges 59 of the I-bars 58 with the depending tongue 60 of the angle block extending downward into the slot between the I-bars. The angle block 41 is vertically apertured to receive a pair of socket head bolts 61 of sufiicient length to extend below the bottom of the jig block tonque 60 and threadingly engage a clamping plate 62. In operation, the jig angle block. 41 is slipped longitudinally between the I-bars 58 until it is positioned the proper distance from the shear 55 to cause the desired length of the strip to be cut, this strip being designated as 63 in the showing of FIGURE 8 and being the longest strip of the stack. The bolts 61 are then tightened to secure the angle block 41 in fixed position by drawing up the clamping plate 62. The remainder of the strips, des ignated as 64, 65 and 66 will then be automatically cut to the proper length by virtue of the angle of the jig block 41. FIGURE 8 shows the fourth strip 66 about to be cut by the shear 55. A side edge guide 67 in the form of an angle bar is seen also in FIGURES 7, 9 and 10 to aid in aligning the side edges of the core strip being cut.

When the strips for a given core section or core have been cut they are removed from the sizing and cutting apparatus 44 and flat stacked in the manner shown in FIGURE 13. This particular arrangement of stacking is effected by end shifting the strips relative to one another so that the ends of the adjacent strips are offset by an amount designated as L in FIGURE 13. This of course causes the opposite ends of these strips to be relatively offset by an amount equal to AC+L. The end offset distance L is a function of the thickness T of the core strip and is chosen to be large relative to the strip thickness in order to minimize the reluctance introduced by the joint created by abutment of opposite ends of each strip of core material. The L/ T ratio is normally chosen to fall between a lower limit to 6 to 1 and an upper limit of 10 to 1, a ratio of 8 to 1 being completely satisfactory for most purposes. Of course, the step ratio may be modified as desired to provide the preferred type of joint configuration illustrated in FIGURES 5 and 6.

With the stack of strip material positioned as illustrated in FIGURE 13, clamping pressure is applied transversely, as for example at the points indicated by the arrows AA, to hold the stack together while it is bent into circular form to thereby form a circular section. It is also to be understood that a plurality of sections may be stacked and simultaneously circularly formed, or alternatively the sections may be individually formed and then internested to provide a composite circular array. Any suitable apparatus may then be employed to shape and anneal the circular array into the finished rectangular form of core as shown, for example, in FIGURE 1.

What is claimed as new and useful is:

1. Apparatus for sizing and cutting one at a time from a continuous supply length of strip core material successively shorter strips of core material stacked in size order and to be subsequently bent into annular circular form with the opposite ends of each strip brought into abutment, comprising in combination, a sizing device including a fiat bed upon which successively cut strips are stacked one upon the other as they are cut and a jig angle block longitudinally shiftably mounted upon said bed and fixedly securable thereto at any desired point along the length of the bed, said jig angle block having a sloping straight planar face oriented to form an acute angle with the surface of the bed to receive within the open end of the angle for abutment with the sloping face of the angle block the leading edge of each strip prior to cutting of the strip from the supply length of strip core material, and a cutting device disposed proximate the end of the fiat bed for shearing off and forming the trailing end of each ship from the supply length of core material after the leading edge of each such strip has abutted the sloping face of the jig angle block, the trailing ends of the strips being disposed substantially in a common plane.

2. The apparatus according to claim 1 wherein the sloping planar face of the said jig angle block forms with the said bed in actute angle whose natural tangent function is less than or equal to 1/ 211-.

3. Apparatus for sizing and cutting one at a time from a continuous supply length of strip core material successively shorter strips of core material stacked in size order and to be subsequently bent into annular circular form with the opposite ends of each strip brought into abutment, comprising in combination, a sizing device including a fiat bed upon which successively cut strips are stacked one upon the other as they are cut and a jig angle block longitudinally shiftably mounted upon said bed and fixedly securable thereto at any desired point along the length of the bed, said jig angle block having a sloping straight planar face oriented to form an acute angle with the surface of the bed to receive within the open end of the angle for abutment with the sloping face of the angle block the leading edge of such strip prior to cutting of the strip from the supply length of strip core material, and a cutting device disposed proximate the end of the fiat bed for shearing off and forming the trailing end of each strip from the supply length of core material after the leading edge of each such strip has abutted the sloping face of the jig angle block, the trailing ends of the strips being disposed substantially in a common plane, said cutting device having upper and lower shearing edges, the shearing engagement line of said cutting device shearing edges where the trailing end of each strip is formed by severance from the supply length of core strip material being spaced vertically above the level of said bed at a fixed elevation at least equal to the thickness of the core stack to be cut.

References Cited by the Examiner UNITED STATES PATENTS 617,787 1/1899 Webb 269-304 X 1,150,291 8/1915 Worthington 83467 1,150,921 8/1915 Worthington 83-467 1,784,556 12/1930 Townsend et al. 83467 FOREIGN PATENTS 467,183 10/ 1928 Germany. 159,723 3/ 1921 Great Britain.

WILLIAM W. DRYER, JR., Primary Examiner.

ANDREW R. JUHASZ, Examiner. 

1. APPARATUS FOR SIZING AND CUTTING ONE AT A TIME FROM A CONTINUOUS SUPPLY LENGTH OF STRIP CORE MATERIAL SUCCESSIVELY SHORTER STRIPS OF CORE MATERIAL STACKED IN SIZE ORDER AND TO BE SUBSEQUENTLY BENT INTO ANNULAR CIRCULAR FORM WITH THE OPPOSITE ENDS OF EACH STRIP BROUGH INTO ABUTMENT, COMPRISING INCOMBINATION, A SIZING DEVICE INCLUDING A FLAT BED UPON WHICH SUCCESSIVELY CUT STRIPS ARE STACKED ONE UPON THE OTHER AS THEY ARE CUT AND A JIG ANGLE BLOCK LONGITUDINALY SHIFTABLY MOUNTED UPON SAID BED AND FIXEDLY SECURABLE THERETO AT ANY DESIRED POINT ALONG THE LENGTH OF TH BED, SAID JIG ANGLE BLOCK HAVING A SLOPING STRAIGHT PLANAR FACE ORIENTED TO FORM AN ACUTE ANGLE WITH THE SURFACE OF THE BED TO RECEIVE WITHIN THE OPEN END OF THE ANGLE FOR ABUTMENT WITH THE SLOPING FACE OF THE ANGLE BLOCK THE LEADING EDGE OF EACH STRIP PRIOR TO CUTTING OF THE STRIP FROM THE SUPPLY LENGTH OF STRIP CORE MATERIAL, AND A CUTTING DEVICE DISPOSED PROXIMATE THE END OF THE FLAT BED FOR SHEARING OFF AND FORMING THE TRAILING END OF EACH STRIP FROM THE SUPPLY LENGT OF CORE MATERIAL AFTER THE LEADING EDGE OF EACH SUCH STRIP HAD ABUTTED THE SLOPING BEING DISPOSED SUBSTANTIALLY IN A COMMON PLANE. 